Could be a Cap coat or a thin coat is sometimes called a skim coat or feather coat
By putting a thin layer of new concrete on top.
That depends entirely on what the finished floor is going to made of. If it's 'click' laminate then wavy thin foam sheet is best. If good quality lino then thin plywood is best , etc.
The corrosion on iron can be reduced by suitable thin layer of element to be electroplated.
A lot depends on the stress factors and use that it's going to get. I've glued pieces to small concrete walls with 'thin set' cement and that works well as long as it's not subject to people jumping on on it like a step. I've also repaired edges of steps this way, but it seldom lasts a year. So far, I haven't found an actual 'glue' that works better with cement than 'thin set' .
You have a major problem. concrete is not water proof (liquid or vapor)or really even water resistent. If you look at a concrete pool or tank, a thin plaster coating provides the water proof layer - not the concrete. Your best bet is to remove the concrete, lay down a real water proof layer and reinstall the concrete. You can put so called water proof paints/materials on the cement, but they will only last a few years. In the mean time, you will have completely rotted the wood framing that supports the concrete slab.
the thin outermost layer of skin is your epidermisThe outermost layer of skin is called Epidermis
The thin layer of the outer Earth is called the crust.
The thin layer of tissue that covers the body of a mollusk is called the "mantle."
Depletion layer is thin now. It is called depletion when the concentration is below 380 Dobson Units.
permafrost
Zest, I am not sure if it's zesting, but I do know a thin layer of orange and lemon peel is called zest.
There is a thin layer of ozone that covers entire surface. It is called ozone layer and protect us too.
The atmosphere surrounds the earth. It is not a thin layer. It is a very thick layer consisting of various gases.
a blastoderm
A coat. Any layer of paint is called a coat. Thick or thin. The first coat is called a base or primer coat.
Global Water
atmosphere